Knowing how to winterize a pool can save you time, money, and frustration once temperatures drop. Whether you own an in-ground or above-ground pool, winterizing ensures your pool survives freezing weather. It’s one of the most important seasonal maintenance steps for any pool owner—and with the right supplies and know-how, you can do it yourself.
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What Does Winterizing a Pool Mean?
Winterizing your pool means prepping it for the off-season by protecting it against freezing temperatures, algae growth, and equipment damage. In simple terms, it’s the process of “putting your pool to bed” for the winter.
While many people use "closing" and "winterizing" interchangeably, they’re not exactly the same. Closing a pool typically applies to warmer regions where freezing isn’t a major concern—it involves cleaning, balancing chemicals, and covering the pool.
Winterizing takes things a step further by draining lines, adding antifreeze, and protecting equipment from ice damage.
The Difference Between Winterizing In-Ground vs. Above-Ground
In-ground pools require line blowing and antifreeze to prevent frozen pipes. Above-ground pools often need an air pillow beneath the cover to absorb expansion and reduce pressure on the pool walls. Both pool types need the right pool chemicals before sealing for the season.
Why Winterizing Your Pool Is Important
It may be hard to imagine ice causing damage to a pool, but it does cause problems. Freezing water expands, which can crack tiles, damage pumps, and burst pipes if left untreated. Taking the time to winterize prevents those costly repairs.
Here’s why winterizing matters:
- Prevents Freeze Damage: Properly draining and adding antifreeze makes sure water doesn’t expand and damage plumbing or equipment.
- Extends Equipment Lifespan: Pumps, filters, and heaters last longer when protected from corrosion and freezing.
- Saves Money: Avoids expensive spring repairs and replacements caused by winter neglect.
- Keeps Water Cleaner: Balanced chemicals and a tight cover help prevent algae blooms, debris buildup, and cloudy water, making reopening faster and easier.
- Improves Safety & Compliance: Following pool maintenance best practices ensures safe handling of chemicals and proper winter storage.
How to Winterize an In-Ground Pool: Step-by-Step Guide
Winterizing an inground pool takes some preparation, but the process is simple once you understand each step.
Step 1: Clean the Pool
Start by giving your pool a deep clean. Use a skimmer net to remove debris like leaves, dirt, and bugs from the surface. Brush the walls, steps, and floor to eliminate buildup, then vacuum thoroughly to remove sediment. A clean pool prevents staining, algae growth, and scaling while the water sits dormant over winter.
Step 2: Balance Water Chemistry
Before adding any winterizing chemicals, test and balance your water. Proper chemistry helps protect your pool’s liner, tile, and equipment during the off-season.
Be sure to check these levels:
- pH: 7.2–7.8
- Total Alkalinity: 80–120 ppm
- Calcium Hardness: 180–220 ppm
If your pH is off, adjust it and balance pH levels. Once balanced, run your pump for several hours to circulate the water evenly.
Step 3: Add Pool Winterizing Chemicals
After your water is balanced, add your pool’s winterizing chemicals. These will keep the water clean, prevent algae, and reduce staining while the pool is closed. Here’s how:
- Chlorine shock to eliminate bacteria and organic matter
- Algaecide to stop algae growth under the cover
- Stain and scale preventer to reduce mineral buildup on surfaces
Follow all label directions for correct dosages.
Step 4: Balance Water Chemistry Again
Recheck your water balance 24 hours after shocking your pool. Chlorine can temporarily affect pH and alkalinity, so testing again ensures stability before closing. Adjust as needed to bring your pH and alkalinity back into ideal ranges; this step is important for preventing corrosion or scaling during the cold months.
Step 5: Add Pool Winterizing Chemicals Again
Before draining or covering, apply a final dose of winter algaecide and stain preventer to give your pool long-lasting protection. These chemicals work throughout the season, preventing algae growth and cloudy water as temperatures fluctuate. Circulate the water briefly after adding them, then shut off your system.
Step 6: Blow Out Lines & Add Antifreeze (if needed)
Water trapped in your pipes can freeze and cause cracks or leaks. Use an air compressor or shop vac to blow air through your pool’s plumbing lines—including the skimmer, return, and main drain until bubbles appear in the pool.
Once the lines are clear, plug each one securely with winterizing plugs. If you live in a cold region, consider adding non-toxic pool antifreeze to your plumbing lines for extra protection.
Step 7: Cover the Pool
Finish by covering your pool with a sturdy winter safety cover or tarp-style cover. Make sure it’s fitted tightly and anchored securely with water bags or straps to prevent wind lift.
A good cover keeps debris, sunlight, and contaminants out, helping your water stay cleaner and making your spring opening much easier.
If your region experiences snow or heavy rain, consider using a cover pump to remove excess water buildup throughout the winter.
Step-by-Step Guide: How to Winterize an Above-Ground Pool
Above-ground pools require a few unique steps to stay protected all winter. The process is similar to winterizing an inground pool but tailored for flexible walls, removable equipment, and exposed plumbing.
Step 1: Clean Pool and Balance Water
Start by removing all debris, leaves, and dirt from your pool. Brush the walls and floor, then vacuum. Clean your filter and skimmer baskets, and remove any lingering residue.
Next, test and balance your water chemistry:
- pH: 7.2–7.6
- Alkalinity: 80–120 ppm
- Calcium Hardness: 180–220 ppm
Balanced water prevents corrosion, scaling, and algae growth during the off-season. Allow your pump to circulate for several hours after adjusting your levels to ensure the chemicals are distributed evenly.
Step 2: Lower Water Levels (if needed)
If you live in an area prone to freezing, lower your pool’s water level to just below the skimmer opening. This prevents freeze-related damage and allows for room to expand. Avoid draining too much water; the liner can shrink or collapse without enough support from the water inside.
Step 3: Protect Skimmer and Return Lines
To keep your skimmer and plumbing lines safe, disconnect hoses and drain all water. Blow out the lines using a shop vac or air compressor to remove moisture that could freeze. Insert winterizing plugs into return fittings and use a skimmer guard. These small devices can prevent major cracks or leaks later.
Step 4: Drain and Store Equipment
Disconnect, clean, and drain your pump, filter, heater, and chlorinator. Store them in a dry, climate-controlled area to protect seals and internal components from freezing temperatures. If you use a cartridge filter, clean and dry the cartridge before storing it flat to prevent warping.
Step 5: Add a Winter Air Pillow
It may sound silly, but an air pillow is an important part of winterizing an above-ground pool. The air pillow absorbs pressure from ice expansion, protecting the pool walls and liner.
Step 6: Blow Out Lines & Add Antifreeze (if needed)
If your pool uses hard plumbing or you live in a cold climate, use a blower to clear all lines. Afterward, pour non-toxic pool antifreeze into the skimmer and return lines as an added safeguard. This step is particularly helpful in regions where extended freezing temperatures are common.
Step 7: Cover the Pool Securely
Place a high-quality winter pool cover over your pool to keep debris out and prevent water contamination.
- For round or oval pools: Use a cable and winch system to tighten the cover evenly.
- For rectangular pools: Use clips or water tubes to secure the edges.
Ensure the cover is snug, but not overly tight. Add a cover pump or siphon to remove excess rain or melting snow throughout the winter.
Pool Winterizing Products: What You’ll Need
Having the right tools and supplies makes winterizing your pool much easier. Here’s what you’ll need to get started:
- Pool shock: Oxidizes contaminants, kills bacteria, and clears cloudy water before closing.
- Algaecide: Prevents algae blooms under your pool cover during the off-season.
- Stain preventer: Helps stop mineral buildup and metal staining.
- Pool antifreeze: Non-toxic formula used to protect plumbing lines from freezing.
- Winter cover: Choose between a tarp-style or safety cover that fits securely and keeps debris out.
- Air pillow: Essential for above-ground pools to absorb ice pressure and support the cover.
- Cover pump or siphon: Removes standing water from the top of your pool cover.
Pool Winterizing FAQs
When should I winterize my pool?
The best time to start winterizing is when the daily temperature consistently drops below 65°F. If you wait too long, falling leaves and cooler nights can impact your water chemistry, making the process harder. In general, aim to winterize before the first frost.
What chemicals are needed to winterize a pool?
Chlorine shock and algaecide are the two most common chemicals needed to winterize a pool.
Do I need to shock my pool before closing it for the winter?
Yes. Shocking your pool before closing helps eliminate bacteria and organic matter that can cause cloudy or green water by spring.
Final Thoughts: Keep Your Pool Protected All Winter
Winterizing your pool might feel like a big task, but with the right products and a step-by-step plan, it’s easy to do yourself. Proper winter care protects your investment, prevents costly repairs, and ensures you’ll dive into clear, clean water come spring.
When you’re ready to start, shop everything you need at ePoolSupply. Our expert team is always here to help you find the best products to keep your pool in top shape all year long.